High frequency sound generator



y 1941- s. KIESSKALT 2,248,459

HIGH FREQUENCY SOUND GENERATOR Filed June 14, 19:9

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AOR

Patented July 8, 1941 HIGH FREQUENCY SOUND GENERATOR Siegfried Kiesskalt, Frankfort on the Main- Hochst, Germany, assignor, by mesne'assignments, to Walther H. Duisberg, New York, N. Y.

Application June 14, 1939, Serial No. 279,122 In Germany May 18, 1938 Claims.

The present invention relates to a high frequency sound generator.

High frequency sound waves of frequencies from about 10,000 cycles per second to inaudible wave frequencies of, say, 1,000,000 cycles per second are produced in gases, liquids or solid bodies either by way of electromagnetically excited ferrous metals by the so-called magnetostriction method, by means of the piezo-electric qualities of quartz crystals, or by means of air whistles. The electrical methods have the drawback that they require complicated electric exciting and stabilizing systems which are generally not as efficient as is desirable. The whistle systems are mechanically simpler but they radiate only little energy.

According to the present invention, high frequency sound waves are produced by easily produced and controlled movements of rotating I wheels, whereby frequencies of 50.to 500 cycles per second corresponding to revolutions or oscillations of about 3,000 to about 30,000 per minute are produced. In this range the speed of the movementsmay readily be kept constant, because large three-phase supply networks may, for instance, directly be used.

According to the invention these wheels, herein called exciting wheels, are bladed at the periphery or at the face and rotate in a liquid, preferably in mercury, for this substance is especially suitable for the transmission of oscillations because of its high density, low viscosity and, in consequence thereof, low damping. Adjacent to the blades of the exciting wheel are arranged the blades of a stationary wheel, which may be constructed as a disk and may be connected with the sound transmitting apparatus or may even itself act as sound transmitter. In the following description, these stationary wheels are, therefore, called transmitting wheels." Both wheels are arranged in the casing or the transmitting wheel serves as a casing, means being provided for causing a rotation movement at least of the exciting wheel, 1. e. a direct rotation of this wheel.

In order to attain high frequencies with the relatively low and readily achieved speeds of revolution at which the wheels are driven, it is advisable that the ratio between the numbers of the blades or teeth of the two wheels should be expressible by the values of me and m wherein n is a whole number and a: and y are two prime numbers closely adjacent to each other. Furthermore, the blades of the transmitting wheel should, if possible, have a natural frequency which corresponds to the product of the number of revolutions of the exciting wheel and the number of blades or teeth of this wheel. The transmitting wheel itself is preferably constructed in such a manner that it has the same natural frequency as basic oscillation. Furthermore, it is advisable to use constructions in which the number of blades of the transmitting wheel pr disk corresponds with the value of z/m, wherein a is the number of nodes of oscillation when the machine is in operation and m is a whole number. For example, if the transmitting wheel is substantially circular it should have, for instance, 16, 32 or 64 teeth or blades according to whether the harmonic is the 4th, 5th or 6th. In this manner an oscillating system of high frequency and relatively great energy is obtained, since the nodal points for the harmonics of the transmitting wheel are known and oscillating energy is supplied at the natural frequency by way of each nodal point, so that the blades are excited in strict tune by shock waves.

The excitation (impulse) is especially strong when cavitation is caused when the flow is directed against the tips of the blades of the transmitting wheel, this being readily effected by using the knowledge gained in the construction of admission turbines, for instance by loading the blades as greatly as possible, by small radius of curvature and the formation of crevices, profiled channels and edges.

Figs. 1 to 3 of the accompanying drawing serves to illustrate, by way of example, two forms of construction of a rotating system according to the invention, but they are notintended to limit it thereto. In the drawing Figs. 1 and 3 are plan views and Fig. 2 is a longitudinal section along the line B-C of Fig. 1.

In Figs. 1 and 2, l is the exciting wheel driven in the direction of the arrow C by way of the shaft 2, and a means IQ for causing rotation, and 3 is the transmitting wheel. The exciting wheel I is provided with blades 4 and the transmitting wheel 3 is provided with blades 5. The driving liquid, preferably mercury, flows between the blades 4 and 5. The mercury passes in the example of Figs. 1 and 2 between the entire outer blade space and an axial channel 6 of the exciting wheel i, an arrangement of blading 1 similar to that of a centrifugal pump in the channel 6 promoting the movement of the liquid. Only the space between the blades 4 of the exciting wheel is first filled with the liquid which flows in the direction of the arrow A. The spaces between the blades 5 of the transmitting wheel are, at

of centrifugal force the liquid is forced to emerge from between the blades I through the crevices 8 only; it is forced into the spaces between the way the impulse is given by the free jets thus produced, otherwise it would be effected by head waves produced by the exciting wheel.

At the lower (outer) end of the blades -5 the liquid emerges and is reconducted to the central channel 6 of the exciting wheel, as indicated by the arrow B, where it is again accelerated. If necessary, the casing 10 in which the transmitting' wheel is located, may be cooled as by borings l3. For improving the cooling action and simultaneously for preventing the formation of mercury vapor, another liquid lighter than mercury, for instance water, may be introduced above the mercury.

For instance. the following numbers yield suitable proportions:

the side at which the stream of liquid enters the spaces, closed by a disk 8. Under the action Number of blades of the transmitting wheeL- 32 Thus the relative prime numbers 15 and 16 are found in the blading of symmetrical rotation. If the exciting wheel is driven at 6,000 revolutions per minute according to a rotary speed of 100 revolutions per second, the blades of the transmitting wheel will have a frequency of 3,000 cycles per second, while according to the blading of the transmitting wheel the fifth harmonic will equal 16 times this value, i. e. 48,000 cycles. In order to avoid transmission losses the blades of the transmitting wheel may be cut out of the mass of the wheel ring or they may be cast.

In many cases a simplified construction of the transmitting wheel 3 will still provide sufficient energy. According to Fig. 3 the transmitting wheel 3 has no blading of its own; the construction of the exciting wheel I with the blades 4 and the pumping channel 6 is the same as in Figs. 1 and 2. The regular shocks caused by the impinging mercury are supplied to the transmitting wheel 3 by means of a guide wheel Ii which is provided with curved channels 12. The number of these channels corresponds with that'of the blades 5 of the transmitting wheel 3 of Fig. 1.

The guide wheel ll closely surrounds the cylindrical exciting wheel I with as small a gap as possible between them. The channels l2 are curved in such a manner that the jets of mercury passing out of the spaces between the blades 4 of the exciting wheel I are collected with as little shock as possible and conducted in a radial direction to the transmitting wheel I, the position of the blade surfaces, therefore, depending on the rotary speed of the exciting wheel. After the exciting shock to the inner surface of the transmitting wheel 3 the mercury fiows ofi freely into the lower part of the casing whence it is again passed via the channel 6 back through the blades 4 to the wheel 3. The smooth, annular construction of the transmitting wheel 3 facilitates easy changing of this part, because adjustment of the position of this member is not necessary when the correct dimensions are maintained. Glass rings or quartz rings may, for instance. be used.

,ural frequency of each blade of the transmitting wheel corresponding with the number of impacts of liquid thrown out per second from the exciting wheel when the machine is in operation, the transmitting wheel acting as a casing, this casing being partly filled with a liquid of high specific gravity and low viscosity, a pumping device arranged so as to circulate the said liquid through the interior of the exciting wheel, the hollow spaces between the wheel and the free space formed by the casing, and means to cause a rotation of the exciting wheel.

2. A high frequency sound generator which comprises an exciting wheel capable of rotating and provided with blades on its circumference and with channels which open between the said blades, a stationary transmitting wheel surrounding the exciting wheel and spaced therefrom and provided with blades on its inner circumference, the number of blades of the transmitting wheel being different from the number of blades of the exciting wheel, the natural frequency of each blade of the transmitting wheel corresponding with one harmonic of the blade frequency of the transmitting wheel, the transmitting wheel acting as a casing, this casing being partly filled with a liquid of high specific gravity and low viscosity, a pumping device arranged so as to circulate the said liquid through the interior of the exciting wheel, the hollow spaces between the wheels and the free space formed by the casing, and means to cause a rotation of the exciting wheel.

3. A high frequency sound generator which comprises an exciting wheel capable of rotating and provided with blades on its circumference and with channels which open between the said blades, a stationary transmitting wheel surrounding the exciting wheel and spaced therefrom and provided with blades on its inner circumference, the number of blades of the transmitting wheel corresponding with the value of z/m, wherein z is the number of nodes of oscillation when the machine is in operation and m is a whole number, the transmitting wheel acting as a casing, this casing being partly filled with a liquid of high specific gravity and low viscosity, a pumping device arranged so as to circulate the said liquid through the interior of the exciting wheel, the hollow spaces between the wheels and the free space formed by the casing, and means to cause a rotation of the exciting wheel.

4. A high frequency sound generator as claimed in claim 1, the circulating liquid being mercury.

5. A high frequency sound generator comprising a rotatably mounted exciting wheel, blades projecting from the periphery thereof, said blades being spaced apart by radial openings terminating in narrow slots, an imperforate stationary transmitting wheel, capable of oscillation, constituting a casing for the generator and being spaced from said exciting wheel to form a containing space for liquid therebetween, inclined blades projecting inwardly from said against the blades of said transmitting wheel to eflect oscillation thereof, said liquid only passing through said slots when said exciting wheel is transmitting wheel so as to lie across the slots in said exciting wheel, said containing space and said radial openings being supplied with a high gravity, low viscosity operating liquid and means for rotating said exciting wheel to force said liquid through the slots of said radial openings rotated.

SIEGFRIED ICIESSKALT. 

